WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2004PR18B
Title: Sorption Behavior of Crumb Rubber to Remove Inorganic and Organic Contaminants from Aqueous Solutions
Project Type: Research
Focus Categories: Water Quality, Toxic Substances, Treatment
Keywords: water treatment, water quality, organic compounds, heavy metals
Start Date: 01/31/2004
End Date: 01/31/2005
Federal Funds: $20,000
Non-Federal Matching Funds: $40,157
Congressional District: N/A
Oscar J. Perales-Perez
University of Puerto Rico
Marco A. Arocha
Protecting water bodies (surface, aquifers and coastal) from contamination is essential for health and safety. Typical inorganic pollutants are heavy metals which form highly soluble solid products (e.g., Hg), or no solid at all (oxyanions like arsenite and arsenate, among others), after treatment of effluents by conventional alkaline precipitation. The limitations of conventional cleaning approaches become more evident when the contaminants are at very dilute concentrations as observed in effluents coming out from water treatment plants using conventional alkaline precipitation, or in ground waters polluted by hazardous species mobilized by leaching and/or percolation throughout soil substrates. Optional solvent extraction and ionic exchange systems are very expensive and they are tailored for high ion selectivity, which limits the removal of all contaminants through a single-step operation.
In Puerto Rico, main problems of heavy metal pollution (mainly by Pb, Cu, Zn and Cd) have been reported in effluents from municipal wastewater, electroplating, metal finishing and printed circuit board manufacturing plants. In turn, the mercury pollution problem in Juncos and the presence of lead in some wells in Gurabo are examples of the aquifers contamination problem issue. The described situation is even more dramatic when the decontamination process deals with hazardous organic compounds, as those reported in some laundries and gas stations in Puerto Rico, where traditional precipitation and ionic exchange processes are not applicable at all. Accordingly, the development of a low-cost, environmental friendly and efficient cleaning process for effluents bearing inorganic and organic contaminants becomes indispensable.
About 4-million tires are discarded annually in Puerto Rico of them, approximately 0.8-million tires are reused each year, and the remainder is land filled, stockpiled or illegally dumped. Land filling is a poor management option for scrap tires. Whole tires take up large amounts of valuable space in a landfill, coming up to surface shortly. New environmental regulations eliminate land filling as a disposal method, greatly increasing the environmental treat of scrap tires. Under this premises, the search of different alternatives to expand the re-use possibilities for scrap tires sounds justified.
The remediation option detailed in this proposal is based on the presence of components in crumb rubber, such as carbon black, zinc oxide, and sulfur, embedded in an elastomeric matrix, with potential capability to absorb/adsorb and precipitate hazardous species (organics and inorganics) from aqueous solution.. The crumb rubber, from scarp tires already cleaned and downsized to different particle sizes, will be utilized in batch experiments to remove different inorganic, such as Cu(II), Cd(II), Hg(II), Cr(III,V) and As (III,V), as well as organic species of environmental concern. Hexane, toluene and trichloroethylene have been chosen as model organic contaminants in this project. We propose to investigate not only the conditions leading to maximization of the uptake capacity and sorption rate for different type of contaminants, but also the conditions needed to re-extract the contaminants (desorption), a factor of critical importance to determine the potential use of the proposed sorbent on a large scale remediation application. Both stages, sorption and desorption, will be modeled, critical parameters determined, and the involved mechanisms discussed in detail.